1. Field of the Invention
The present invention relates to a three dimensional display apparatus that displays true three dimensional images that can be viewed without the use of three-dimensional eye glasses.
2. Description of the Prior Art
Three-dimensional images improve the visual effects of video devices such as movies, televisions, video games, computer graphics, and radar imaging devices. Numerous display devices have been proposed to provide three-dimensional images. One type of prior art display device uses specially-designed "three-dimensional" or stereo vision glasses for simulating three-dimensional images on a two-dimensional display screen. This type of device is unsatisfactory because viewers often object to wearing the special glasses, especially viewers who already wear vision correcting eyewear.
Other types of prior art display devices use vibrating mirrors or multiple, stacked two-dimensional screens to display three-dimensional images. While these types of devices create actual three-dimensional displays, they have not been commercially successful because of high costs, poor reliability and poor resolution.
Another type of prior art display device separates the information from a three-dimensional image into several two-dimensional planes. The two-dimensional planes are then individually generated on a CRT screen while the CRT screen is moved back and forth to different depth locations. This type of display requires the focusing parameters of the system to be continuously adjusted electromechanically as the screen is moved back and forth. Additionally, the mechanical system that moves the CRT screen successively stops and restarts the screen at each of the endpoints of the viewing region, and in doing so, generates excessive noise and vibration. Specifically, the screen moving system for this type of prior art display consists of a mechanical cam system including a plurality of wheels each having a diameter equal to the size of the display depth space, a pair of linear slides that move the distance of the depth space, and a long rod coupled between the wheels and the slides for moving the slides back and forth as the wheels rotate. This type of screen moving system is large and heavy and generates excessive noise and vibration during operation.
Another known type of three-dimensional display uses laser beams and high-precision optical components to access pixels on a rotating helical screen. Although this type of device is much quieter than the previously described display, it is extremely expensive and therefore not practical for most uses. Additionally, this type of device can access only a small, fixed number of pixels over a three-dimensional volume.